The present invention relates to a sterilization and/or sanitization process and apparatus for containers used for aseptic packaging of products or ingredients sensitive to microbiological spoilage or contamination. The present invention is particularly useful in sterilizing or sanitizing polyethylene terephthalate (PET) containers, especially those with openings of a relatively small cross-sectional area compared to total internal surface area and those formed of non-heat set PET.
For the purposes of this disclosure, sterilization is defined as a 6 log reduction of spores of the bacteria Bacillus subtillis var. globigii, whereas sanitization is defined as a 5 log reduction of organisms that cause spoilage of high acid products (i.e., a pH of 4.6 or less), as typified by ascospores of the yeast Saccharomyces cerevisiae. Sanitization can be utilized for containers that are designed or used to store high acid products (e.g., juices, juice beverages, acidified products), whereas sterilization is preferably utilized for containers that are used to store low acid products (e.g., tea, coffee, dairy products, nutraceuticals, pharmaceuticals).
Various apparatuses and methods for sterilizing or sanitizing containers are known. The known apparatuses and methods often use a sterilant such as hydrogen peroxide (H2O2) vapor. After the hydrogen peroxide vapor is discharged into the container at a relatively high temperature, the residual sterilant is then purged from the container with a hot air flush at high temperatures.
However, these known apparatuses and methods are not suitable for containers made of certain materials, such as PET and, more particularly, non-heat set PET. For example, it is difficult to eliminate residual sterilant, such as hydrogen peroxide, not only from the surface of the PET container, but also from its polymer matrix. Upon dosing of hydrogen peroxide into a non-heat set PET container, some peroxide becomes trapped in the polymer matrix and is not readily removed with the hot air flush. Although this can be quite stable for several minutes to hours, when a fluid product is introduced into the container, the hydrogen peroxide moves from the polymer matrix into the body of the fluid product, potentially compromising federal regulations for limits on peroxide residuals.
In addition, because of the relatively low vapor pressure of hydrogen peroxide at temperatures below 250xc2x0 F., most existing sterilization processes depend on the use of a flush using large volumes of a gas that has been heated to a temperature well above 250xc2x0 F. Because non-heat set PET possesses a glass transition temperature of 163.4xc2x0 F., it is not possible to expose such containers to temperatures much above 163xc2x0 F. without risk that the containers will deform. Furthermore, the size of the opening (finish) in many containers prohibits the flow of measurably large volumes of air into and out of the containers within the short period of time required for high-speed operation.
The present invention provides an apparatus and method that can sterilize or sanitize a variety of containers in a fast, economical way.
The present invention further provides an apparatus that can sterilize or sanitize containers on a mass scale, yet occupies a relatively small area.
The present invention can effectively sterilize or sanitize PET containers without deforming the containers.
The present invention can also sterilize or sanitize PET containers leaving an amount of residual sterilant that does not exceed 0.5 mg/l in a container filled with water immediately after treatment. This value is equal to or less than the limits for sterilant residual dictated by the U.S. Food and Drug Administration (FDA).
The present invention provides a sterilization and sanitization method and apparatus for rapidly and relatively inexpensively sterilizing or sanitizing any type of standard container used for packaging of pharmaceuticals, nutraceuticals, health enhancing products as well as traditional high and low acid foods.
According to one aspect of the present invention, a method of sterilizing and/or sanitizing a container includes the steps of generating a sterilant vapor and positioning a nozzle through an opening in the container and no closer than 15 mm from any internal surface of the container that is perpendicular to a principal direction of flow of sterilant vapor through the nozzle. The method further includes the steps of discharging the generated sterilant vapor through the nozzle and into the container and purging the container of the discharged sterilant.
According to another aspect of the present invention, a method of sterilizing and/or sanitizing a container, the container having an opening of a predetermined diameter, with a ratio of the interior surface area of the container to the cross-sectional area of the opening being at least 7.5, includes the steps of generating a sterilant vapor and positioning a nozzle through the opening in the container, the nozzle having a diameter no greater than one-half the predetermined diameter of the opening of the container. The method further includes the steps of discharging the generated sterilant vapor through the nozzle and into the container and purging the container of the discharged sterilant.
According to yet another aspect of the present invention, a method of sterilizing and/or sanitizing a PET container includes the steps of generating a sterilant vapor having a temperature no greater than 160xc2x0 F. and positioning a nozzle through an opening in the container. The method further includes the steps of discharging the generated sterilant vapor through the nozzle and into the container and purging the container of the discharged sterilant with a heated gas having a temperature no greater than 160xc2x0 F., wherein the purging step is completed no longer than 30 seconds from a beginning of the discharging step.
According to still another aspect of the present invention, an apparatus for sterilizing and/or sanitizing a container includes a generator of sterilant vapor, a nozzle communicating with the generator and a positioning mechanism for positioning the nozzle through an opening in the container and to a position no closer than 15 mm from any internal surface of the container that is perpendicular to the principal direction of flow of the sterilant vapor. The apparatus further includes a controller for controlling discharging of the generated sterilant vapor through the nozzle and into the container and purging the container of the discharged sterilant.
According to still yet another aspect of the present invention, an apparatus for sterilizing and/or sanitizing a container, the container having an opening of a predetermined diameter, with a ratio of the interior surface area of the container to the cross-sectional area of the opening being at least 7.5, includes a generator of sterilant vapor and a nozzle communicating with the generator, the nozzle having a diameter no greater than one-half the predetermined diameter of the opening of the container. The apparatus further includes a positioning mechanism for positioning the nozzle through the opening in the container and a controller for controlling discharging of the generated sterilant vapor through the nozzle and into the container and purging of the container of the discharged sterilant.
According to another aspect of the present invention, an apparatus for sterilizing and/or sanitizing a PET container includes a generator of sterilant vapor having a temperature no greater than 160xc2x0 F., a nozzle communicating with the generator and a positioning mechanism for positioning the nozzle through an opening in the container. The apparatus further includes a controller for controlling discharging of the generated sterilant vapor through the nozzle and into the container and purging of the container of the discharged sterilant with a heated gas having a temperature no greater than 160xc2x0 F. The controller controls purging to be completed no longer than 30 seconds from discharging of the sterilant.
According to yet another aspect of the present invention, a method of sterilizing and/or sanitizing a container includes the steps of generating a sterilant vapor, discharging the generated sterilant vapor into the container and purging the container of the discharged sterilant with heated gas. Reduction of Bacillus spores in the container by a predetermined amount X (log) is effected by satisfying the following equation:
X=(0.138xc3x97a/b)+(0.066xc3x97T1)xe2x88x92(0.00083xc3x97c/b)+(0.021xc3x97T2)+(0.008347xc3x97d)xe2x88x9211.357, 
wherein
a is the mass of discharged sterilant vapor (mg),
b is the container volume (1),
c is the volume of purging gas (1),
d is the ambient relative humidity (% RH),
T1 is the temperature of the discharged sterilant vapor (xc2x0 F.), and
T2 is the temperature of the purging gas (xc2x0 F.).
According to yet another aspect of the present invention, a method of sterilizing and/or sanitizing a container includes the steps of generating a sterilant vapor and discharging the generated sterilant vapor into the container. The method further includes the step of purging the container of the discharged sterilant with heated gas, wherein reduction of yeast ascospores in the container by a predetermined amount Y (log) is effected by satisfying the following equation:
Y=(0.063xc3x97a/b)+(0.023xc3x97T1)xe2x88x92(0.00036xc3x97c/b)+(0.052xc3x97T2)+(0.009xc3x97d)xe2x88x923.611, 
wherein
a is the mass of discharged sterilant vapor (mg),
b is the container volume (1),
c is the volume of purging gas (1),
d is the ambient relative humidity (% RH),
T1 is the temperature of the discharged sterilant vapor (xc2x0 F.), and
T2 is the temperature of the purging gas (xc2x0 F.).
According to still another aspect of the present invention, a method of sterilizing and/or sanitizing a container includes the steps of generating a sterilant vapor, discharging the generated sterilant vapor into the container and purging the container of the discharged sterilant with heated gas. Reduction of the sterilant in the container to a predetermined amount Z (mg/l) is effected by satisfying the following equation:
Z=(0.030xc3x97a/b)xe2x88x92(0.043xc3x97T1)xe2x88x92(0.040xc3x97c/b)xe2x88x92(0.075xc3x97T2)+15.747, 
wherein
a is the mass of discharged sterilant vapor (mg),
b is the container volume (1),
c is the volume of purging gas (1),
T1 is the temperature of the discharged sterilant vapor (xc2x0 F.), and
T2 is the temperature of the purging gas (xc2x0 F.).